Some conventional exhaust gas desulfurization systems provided for exhaust gas treatment in a thermal electric power plant etc. use what is called a liquid column type gas-liquid contact apparatus in which absorbent slurry is brought into contact with exhaust gas to absorb sulfur oxides in exhaust gas as disclosed in Unexamined Japanese Utility Model Publication No. 59-53828.
In the gas-liquid contact apparatus used for the desulfurization system of this type, a spray pipe, which is provided with a plurality of nozzles in the lengthwise direction and whose one end is closed, is arranged horizontally in a contact treatment tower (absorption tower) through which gas passes vertically so that a liquid is supplied from the other end of this spray pipe and injected upward, by which the liquid is brought into contact with the gas to perform treatment.
Usually, a plurality of the aforementioned spray pipes are arranged in parallel over the transverse range in the contact treatment tower, and a supply pipe, to which the other ends of these spray pipes are connected at plural places in the lengthwise direction, whose one end is closed, and from the other end of which the liquid is supplied, is provided outside the contact treatment tower. Thereby, the liquid is supplied to each spray pipe via this supply pipe.
The aforementioned spray pipes and supply pipe are conventionally formed of a pipe having a constant cross section in the lengthwise direction, so that the flow passage cross section is constant in the lengthwise direction.
In the conventional gas-liquid contact apparatus of this type, as shown in FIG. 7, the blow-up state of liquid from several nozzles on the closed end side, of the nozzles provided on the spray pipe, is disturbed greatly, so that the blow-up heights thereof vary and decrease remarkably on an average as compared with the blow-up heights of liquid from other nozzles. If the blow-up state is bad as described above and the scattering of liquid is insufficient at some places, some of exhaust gas passing through the contact treatment tower scarcely comes in contact with the liquid (absorbent slurry) in the tower, so that the desulfurization percentage decreases extremely in the case of the desulfurization system.
There is a method in which in order to maintain a high desulfurization percentage forcedly, the entire supply quantity of liquid is considerably increased to make the scattering state in this place sufficient. However, with this method, the quantity of liquid supplied to the remaining nozzles increases wastefully, resulting in the increase in operation cost.
Also, in the conventional gas-liquid contact apparatus, in addition to the above-described nonuniform blow-up state of one spray pipe, nonuniformity of blow-up heights occurs between individual spray pipes. Specifically, in the lengthwise direction of the supply pipe as well, the blow-up state of spray pipes closer to the closed one end of the supply pipe is unstable, and the blow-up heights thereof reversely become great as compared with the other spray pipes.
Assuming that Bernoulli's theorem holds macroscopically for the average value of flow velocity etc., the blow-up height is thought to be approximately proportional to the static pressure. Therefore, it is thought that as the position comes closer to the closed one end of the spray pipe or supply pipe, the flow rate (dynamic pressure) decreases and the static pressure increases, by which the blow-up height is increased.
However, in the lengthwise direction of spray pipe, contrary to this theorem, actually the blow-up heights at the downstream-side nozzles are low on an average as described above, being nonuniform.
Also, the position of the inner face of end plate for closing one end of spray pipe is conventionally set at the outside position far distant from the position of the maximum inlet inside diameter of nozzle positioned closest to the closed end of spray pipe as indicated by reference numeral 61a in FIG. 10.